Differential pressure device for folding apparatus

ABSTRACT

A folding apparatus is provided with a pivotal folding punch that moves past a work sheet supporting surface and an anvil. Hydraulically powered piston and cylinder mechanisms pull the anvil against the work sheet supporting surface while simultaneously pulling the punch about the anvil. Second hydraulic cylinder and piston mechanisms provide a variable resistance force against the movement of the punch.

United States Patent n 1 nu 3,875,784

Daniels Apr. 8, 1975 [54] DIFFERENTIAL PRESSURE DEVICE FOR 3.388.5746/[968 lgnoffo 72/22 3.581.535 (lll ll Hlllkh' .a 72/3]:

{75] Inventor: Dennis Daniels, Bcllcvue. Wash. Prim)? w. Lanhum [73]Assignee: U.S. Amada l.td.. Seattle. Wash. AMI shrill I.\'umi1m'M. J.Keenan [22 Filed: Mar 4' I974 Agcnr. or Fn'mSeed. Berry, Vernon ('51 21Appl No.: 448.037

I57] ABSTRACT 2% 72/320: n/Dlb 72/313 A folding apparatus is providedwith a pivotal folding l 7 4 2 punch that moves past a work sheetsupporting sur- 8] held of 1: face and an anvil. Hydraulically poweredpiston and LIDIG' 8 cylinder mechanisms pull the anvil against the worksheet supporting surface while simultaneously pulling [56] f f (Med thepunch about the anvil. Second hydraulic cylinder UNITED PATENTS andpiston mechanisms provide a variable resistance 2.228.448 H194! Fatlur72/3l9 force against the movement of the punch. 3 l)l)9 2()l ll/WhlHansen 71/322 l 3.209.570 m/whs Hills 72m 6 Ualm- 3 Drawmg FguresDIFFERENTIAL PRESSURE DEVICE FOR FOLDING APPARATUS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates tonumerically controlled, automatic folding machines and. moreparticularly. to means for adjusting the clamping pressure between theanvil and the work sheet supporting surface on such folding machines.

2. Description of the Prior Art In my earlier application. Ser. No.186.062. filed Oct. 4. l97l. now US. Pat. No. 3.815.393. there isdisclosed a sheet metal forming maching of the type having a work sheetsupporting surface. At the end of the supporting surface and spacedtherefrom is a movable anvil. A movable folding punch is pivotallymounted on the machine to pivot past the end of the anvil and the worksheet supporting surface to bend the sheet metal around the anvil. Theclamping force between the anvil and the work sheet supporting surfaceis automatically provided by a pair of hydraulic cylinders and pistons.The cylinders are mounted on slides that are secured to the ends of theanvil and the piston rods are coupled by chains to the punch. Retractionof the piston rods first pulls the anvil down into engagement with thework sheet and then draws the punch up and around for the bendingoperation. Many different types of mechanisms could be provided forobtaining the combined clamping and punching action. but. for thepurposees of this invention. it only need be understood that the greaterthe pull on the pivotable punch. the greater the clamping force.

sheet metal. of course. comes in many different thicknesses and degreesof ductility. and the same machine will be required to fold thick V4inch) steel plates and 1/32 inch aluminum sheets. lfthe clamping load isdesigned for tough steel. the anvil will press the steel with a largeforce to prevent slippage during bending. However. this same clampingforce is then also applied on soft aluminum sheet prior to the punchbeginning its bending action. In such a case. the clamping pressure maybe too great. leaving an impression in the aluminum due to the excessiveclamping force.

SUMMARY OF THE INVENTION It is an object of this invention to provide avariable differential pressure device for varying the clamping force ona work sheet in a pivotable. punch-type folding machine.

It is another object of this invention to provide an automatic foldingmachine in which the clamping force can be readily varied. dependentupon the type of work sheet being folded.

Basically. the invention employs hydraulically powered resistance meansthat oppose the force tending to pivot the punch about the anvil.Control means are provided for varying the amount of the resistanceforce. In the preferred embodiment. the resistance force is provided bya pair of hydraulic cylinder and piston mechanisms. the piston rodsbeing operatively connected to the ends of the folding punch. A variablepressure relief valve is in the hydraulic line discharging from thecylinder when the punch is being moved about the anvil so that. byvarying the relief pressure. the amount of resistance is determined.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric ofa preferredfolding machine embodying the principles of the invention.

FIG. 2 is a vertical section of the folding machine shown in FIG. 1.

FIG. 3 is a preferred hydraulic schematic embodying the principles ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As best shown in FIG.I. the folding apparatus includes a base frame 10 having side frames 12and 14 and a work piece supporting surface 18. The work piece supportingsurface is provided with adjustable stops 22 for moving a work sheetupwardly thereon. An anvil 23 is fixed at either end to a pair of slides24 that ride in guides 25 mounted on the side frames 12 and 14. Theanvil is movable upwardly a slight distance from the work piecesupporting surface 18 so that a work sheet W can be moved beneath. Theanvil can then be moved toward the supporting surface 18 to tightlyclamp the work sheet during the folding operation.

Folding is accomplished by a pivotable punch 26 of the type described inmy earlier application which is mounted to pivot about an axis 27.

The punch is simultaneously pivoted with additional clamping force beingapplied to the work sheet by a pair of hydraulic cylinders and pistons30. For this purpose the cylinders are pivotally mounted by brackets 32to the slides 24 which are coupled to the anvil 23. The piston rods 34are coupled by chains 36 to the end of the punch by studs 38. As isreadily apparent. retraction of the piston rods into the cylinders 30first pulls the anvil 23 downwardly to clamp the work sheet and thence.with further retraction. draws the punch 26 about the end of the anvilto fold the work sheet. As is well known. the anvil is provided with afolding edge 23a to provide a crease in the work sheet.

For the purpose of providing a variable resistance against pivotablemovement of the punch 26, a second set of cylinders and pistons 40 areprovided. one on each side of the machine. Piston rods 42 are eachcoupled by a pivotable clevis 44 to the punch 26. As is readilyapparent. movement of the punch in a counterclockwise direction. asshown in FIG. 2, will cause the piston rods 42 to be extended in thecylinders 40.

FIG. 3 illustrates a preferred hydraulic circuit for varying the amountof resistance force supplied by the piston rods 42. A pump P driven by amotor M delivers pressurized fluid to a solenoid-controlled,spring-biased valve 50. In the deenergized position. valve 50 directsfluid to line 51 to a three-way. spring-centered. solenoid-controlledvalve 52. In the center position. the line 51 is connected to sump.Movement of valve 52 to the right directs line pressure from 51 to aline 53 and thence to the piston rod ends 34 of the cylinders 30. Thepiston rods 34 begin to retract but movement is resisted by piston rods42, thus pulling the cylinders 30 and slides 24 downwardly to place aninitial clamping force on the work sheet as described earlier. Fluidtrapped in the piston rod ends of the cylinders 40 passes through lines54 to a solenoid-operated valve 60 which. when energized. passes thefluid to a line 61 which is directed to sump through a pressure reliefvalve 62. This pressure relief valve is of any conventional type whichcan be adjusted to open to sump through a range of 5 to 500 psi.Assuming valve 62 is set to open at a pressure of (if) p.s.i.. forexample. the punch 26 will be unable to pivot until such time as theclamping force exceeds the 60 psi. resistance force of the piston rods42. Once this pressure is exceeded. additional clamping force isapplied. dependent on the resistance to bending of the material of thework sheet. By changing the setting of valve 62. it can be readily seenthat the initial clamping force can be easily varied from low forces forsoft materials to large forces for tough materials.

The rate of punch movement is controlled by a flow restriction valve 70and a two-way. spring-return solenoid valve 75. When valve 52 is to theright. retracting piston rods 34. valve 75 is moved to the left. causingfluid from the head ends of cylinders 30 to pass through check valve 72and thence through the flow restriction valve 70. The valve 711 permitsfluid to leave the cylinders at a controlled rate.

The piston rods 42 are retracted while simultaneously extending thepiston rods 34 (and returning the punch} by moving the valve 52 to theleft and valve 75 to the right. as shown in FIG. 3. In this position.line pressure front line 51 passes through valve 75. thence b throughcheck valve 72 to lines 54. moving the piston rods 42 to the right. Themovement of piston rods 42 to the right pulls the punch back down.causing the piston rods 34 to be extended through chains 36. Valve 72opens only after a slight. predetermined pressure is reached. so thatfluid moves piston rods 42 prior to piston rods 34. thus assuringtension in the chains 36.

While preferred embodiments of the invention have been illustrated anddescribed. it should be understood that variations will be apparent toone skilled in the art without departing from the principles of theinvention.

The embodiments of an invention in which a particular property orprivilege is claimed are defined as follovvs:

l. A variable load applying apparatus for a fluidoperated foldingmachine of the type having a frame provided with a work sheet supportingsurface. an anvil spaced from said work sheet supporting surface. toallow free movement of a work sheet beneath and having a folding edge. apunch mounted for pivotal movement past said work sheet supportingsurface and folding edge to bend a work sheet clamped between the anviland work sheet supporting surface. first powered means for moving theanvil toward said work sheet supporting surface for clamping a worksheet therebetween and for moving said punch to bend the work sheet. andwherein the clamping force is varied directly with the punch bendingforce. the improvement com prising:

means for providing a variable resistance force against movement of saidpunch so that initial movement of said first powered means effects avariable clamping force on the work sheet dependent on said resistanceforce. and

variable control means for determining the resistance force.

2. The apparatus of claim 1. said means for providing a variableresistance force including second powered means flexibly coupled to saidpunch.

3. The apparatus of claim I, said first powered means including flexiblecoupling means secured to opposite ends ofsaid punch, said secondpowered means including second flexible coupling means secured toopposite ends of said punch. said first and second powered meansincluding hydraulic means for providing simultaneously opposed forces onsaid punch for controlling pivotal movement of the punch.

4. The apparatus of claim 3, said folding machine including transverselyspaced. upright side frames having guide slots therein. said firstpowered means including cylinders and piston rods. linkage meanspivotally securing each cylinder to said anvil. said flexible couplingmeans secured between the piston rods and said punch whereby retractionof said piston rods pulls said cylinders against said linkage means topush said anvil against said work piece supporting surface.

S. The apparatus of claim 2, said cylinders and piston rods coupledbetween the punch and said frame. said second powered means includingforce resistance means for providing a variable resistance forceincluding hydraulic flow lines coupled to said cylinders. said controlmeans including a pressure relief valve coupled to said hydraulic flowlines for relieving fluid pressure in said cylinders to extend thepiston rods and thus allow movement ofthe punch. only after theresistance force exceeds a predetermined amount.

6. The apparatus of claim 5. said first powered means including primarycylinders and piston rods and bydraulic lines to said cylinders. saidcontrol means ineluding main control valve means for directing flow tosaid primary cylinders to begin moving the anvil against the work sheetand thence pivoting the punch at a con

1. A variable load applying apparatus for a fluid-operated foldingmachine of the type having a frame provided with a work sheet supportingsurface, an anvil spaced from said work sheet supporting surface, toallow free movement of a work sheet beneath and having a folding edge, apunch mounted for pivotal movement past said work sheet supportingsurface and folding edge to bend a work sheet clamped between the anviland work sheet supporting surface, first powered means for moving theanvil toward said work sheet supporting surface for clamping a worksheet therebetween and for moving said punch to bend the work sheet, andwherein the clamping force is varied directly with the punch bendingforce, the improvement comprising: means for providing a variableresistance force against movement of said punch so that initial movementof said first powered means effects a variable clamping force on thework sheet dependent on said resistance force, and variable controlmeans for determining the resistance force.
 2. The apparatus of claim 1,said means for providing a variable resistance force including secondpowered means flexibly coupled to said punch.
 3. The apparatus of claim1, said first powered means including flexible coupling means secured toopposite ends of said punch, said second powered means including secondflexible coupling means secured to opposite ends of said punch, saidfirst and second powered means including hydraulic means for providingsimultaneously opposed forces on said punch for controlling pivotalmovement of the punch.
 4. The apparatus of claim 3, said folding machineincluding transversely spaced, upright side frames having guide slotstherein, said first powered means including cylinders and piston rods,linkage means pivotally securing each cylinder to said anvil, saidflexible coupling means secured between the piston rods and said punchwhereby retraction of said piston rods pulls said cylinders against saidlinkage means to push said anvil against said work piece supportingsurface.
 5. The apparatus of claim 2, said cylinders and piston rodscoupled between the punch and said frame, said second powered meansincluding force resistance means for providing a variable resistanceforce including hydraulic flow lines coupled to said cylinders, saidcontrol means including a pressure relief valve coupled to saidhydraulic flow lines for relieving fluid pressure in said cylinders toextend the piston rods and thus allow movement of the punch, only afterthe resistance force exceeds a predetermined amount.
 6. The apparatus ofclaim 5, said first powered means including primary cylinders and pistonrods and hydraulic lines to said cylinders, said control means includingmain control valve means for directing flow to said primary cylinders tobegin moving the anvil against the work sheet and thence pivoting thepunch at a controlled rate.